Frequency multiplier



July 13, 1937. J. EVANS FREQUENCY MULTIPLIER Filed Nov. 30, 1934INVENTOE QQSQQ ERIE basi .8

description when'read in connection'with the 35 and of a shunt connectedvariable capacitor Patented July 13, 1937 UNITED STATES FREQUENCYMULTIPLIER John Evans, Riverside, N. J., assignor, by mesne assignments,to Radio Corporation of America,

New York, N. Y., a

corporation of Delaware Application November 30, 1934, Serial No.755,392

8 Claims.

This invention relates to frequency multipliers and more particularly toa device in which frequency multiplication is obtained by ,suitablecontrol of an electron beam in a cathode ray tube whereby a fundamentalfrequency impressed upon the deflecting circuits of such a tube may bemultiplied to any desired frequency, harmonic or otherwise.

My invention has particular utility in ultra high frequency work. It hasbeen found very diflicult to economically obtain satisfactory frequencystabilization of ultra high frequencies. My solution of the problemenables one to use a crystal-controlled oscillator or any otheroscillator of a fundamental frequency which can be accurately regulatedand then to develop oscillations of any desired harmonic frequency undercontrol of the fundamental frequency. The apparatus for accomplishingthis result is so characterized that the fundamental frequency may bemultiplied many fold. The desired factor of multiplication is obtainedby suitable design of one of the electrodes in a cathode ray tube. For agiven tube this factor remains invariable, although, according to onemodification of my invention presently to be described, a choice betweenseveral factors may be had.

In carrying out my invention I have chosen to utilize a cathode ray tubebecause it provides a dependable means for multiplying the frequency ofany desired fundamental source without resort to apparatus having anymovable mass. My application of the cathode ray tube, therefore,provides further evidence of the many advantageous r uses to which sucha device maybe put.

As is well known, energy can be so applied to the deflection of afocused beam of electrons as to produce a motion which is substantiallydevoid of inertia.

It is among the obj'ectsof my invention to provide a frequencymultiplier of the type. hereinabove suggested in which any desiredfactor of multiplication may be obtained.

It is anotherobject'of my invention to provide a frequency multiplier inwhich currents of considerable amplitude andat ultra high fre-' quencymay be generated. Y

Still another object of my invention is to proa vide suitable apparatusfor stabilizing; an ultra high frequency current. v

The foregoing and other objects and advantages of my invention will bemore clearly understood uponreference to the following detailedaccompanying drawing in which Figure 1 shows diagrammatically thecircuit arrangements and electrode arrangements for a cathode ray tubeas used in my invention, and

Fig. 2 is a plan view of a modified form of one of the electrodes suchas may be used in the cathode ray tube otherwise shown in Fig. l.

Referring now to Fig. 1, I show a specially constructed cathode ray tubel, the envelope of which contains a usual cathode 3 having, if desired,a separate heater element 5, a beam focusing anode I, an acceleratinganode 9, and further accelerating electrodes, l3 and 15. Beam deflectingmeans may beprovided in the form of electrostatic plates l1 and [9 forhorizontaland vertical deflection respectively. In place of theelectrostatic plates, magnetic deflecting coils (not shown) may beprovided, if desired. In either case, the deflecting elements areincluded in circuits from a single-phase or polyphase source of energy.If a single-phase so'iirce only is available, 'as shown at 2!, then aphase shifting device 23 may be provided in one of the circuits whichincludes the deflecting means ll. One of the electrostatic plates [l andalso one of the plates l9 may, if desired, be grounded as at 25. Inorder to control the amplitude of beam defiection I may provide arheostat 21 having a movable tap 29 which is also grounded.

The action of the cathode ray tube. insofar as it is controlled by theelectrodes thus far described, is such as to project a beam of electronsrotatably-against the target electrode ll. Some of the electrons in thestream are, therefore, permitted to accelerate through the apertures 3|and to continue their course in the direction of the electrode l3.sharply focused that substantially the full force of the electron gunwill be directed at one time through a single hole 3! and next againstthe wall of the target ll adjacent two of the holes. The beam is,therefore, intermittently intercepted. The electrons emergeintermittently on the other side of the target H and are furtherdirectedand controlled in their course back and :forth in thecylindrical zone bounded by the electrodes ll andl3 at the two endsthereofand by acircumferential' electrode l5 which is preferably locatedmid-way between the other two. A source of direct current 33 is providedin connection with the electrode {5 so as to render a The electron beamis so 31. A mid-tap on the inductance 35 connects with the negative sideof the source 33. Suitable potentials are applied between the remainingelectrodes of the cathode ray tube as indicated at 39, M and 43,respectively.

It has been found desirable to provide still further means for directingthe course of the electrons after they have emerged from the orifices 36so that their paths shall be substantially parallel with the axis of theelectron gun up until they are attracted to the ring-shaped anode l5.Such a means may comprise a magnetic coil d5 so surrounding the enlargedcylindrical portion of the cathode ray tube I as to produce a magneticfield having its lines of force substantially parallel to the tube axis.Any suitable energizing source such as the battery 41 may be providedfor the coil 65. The velocity of the electrons is made such that thesecondary electrons emitted by the impact of the primary electronsprogress back and forth repeatedly between the electrodes ii and i3,gradually releasing more and more electrons from these emissive elementsuntil the beam itself attains considerable magnitude compared with thatof the beam projected by the electron gun. It is, therefore, possibleunder these circumstances to control the generation of oscillations ofultra high frequency in an output circuit which includes the shuntconnected impedance 35 and capacitor 31, this result being obtained bythe employment of comparatively low power applied to the electron gunand to the defiecting circuits. The increase in power output isderived'largely from the source 33 which has no efiect upon the actionof the electron beam prior to its emergence through the apertures 3iAccording to a modification of my invention as shown in Fig. 2, thetarget Ha may be provided with apertures of diiferent shapes and sizesso that different factors of multiplication may be obtained by merelycontrolling the radius of curvature of the electron beam as it isintercepted by this target. Thus suitable adjustment of the rheostat21-29 enables one to vary the deflecting force as applied both to thehorizontal and to the vertical deflecting elements simultaneously. Thecircular path of the electron beam is, therefore, maintained; but in onecase if its radius is as shown at r, a low factor of multiplication willbe obtained because only the apertures 3la extend to Within this radius.If the deflecting force is increased to an intermediate value, then thepath of the electron beam may have a radius r so as to comprehend boththe apertures 3i... and additional apertures 3'11. With the employmentof a maximum deflecting force, the radius of the electron beam may beincreased to 1 thereby comprehending all of the apertures in the targetHa including apertures 3h, 3 lb and Me. Thus different factors ofmultiplication may be obtained at will.

It is apparent that upon the employment of 7 any fundamental frequency amultiplication of that frequency may be obtained, the factor ofmultiplication being determined solely by the aoeaoos Utilization of themultiplied frequency may be had by suitable connections or coupling withthe output circuit in any well known manner.

Although I have disclosed herein certain specific means foraccomplishing the objects of my invention, these are given merely by wayof example and are not to be construed as limitations to the scope of myinvention. It will be apparent to those skilled in the art that myinvention is not thus limited, but many modifications may be madewithout departing from the scope of my invention as set forth in theappended claims.

I claim as my invention 1. In a device of the class described, anelectron discharge tube, an apertured electrode separating two portionsof said tube and including therein a plurality of equally spacedapertures uniformly disposed with respect to the center of saidelectrode, means including other electrodes in one portion of said tubefor projecting a stream of electrons successively through differentapertures in the first said electrode and into the other portion of saidtube, additional electrodes in the last said portion of said tube, aresonant output circuit connected between one of the last saidelectrodes and the apertured electrode for producing secondary emissionunder control of the stream of electrons first mentioned, wherebyoscillations of high frequency and high power are set up and a source ofpolarizing potential connected between another of said additionalelectrodes and a point intermediate the ends of said resonant outputcircuit.

2. Apparatus in accordance with claim 1 further characterized in thatthe first mentioned electrode and one other electrode of the tubeportion into which the electron stream is last projected are madeemissive and another of said additional electrodes is a ring shapedanode interposed between said emissive electrodes, and chargedpositively with respect to said emissive electrodes.

3. In an oscillation generator, a cathode ray tube having heater,cathode, and focusing electrodes of the electron gun type and havingboth horizontal and vertical beam deflecting means, and a plurality ofadditional electrodes for producing an accelerating electronic emissionbeyond the zone of beam deflection, one of said additional electrodeshaving a plurality of apertures concentrically spaced and increasing innumber with increasing distances from the center of said electrode andbeing so related as to alternately intercept and pass electronstherethrough, means for producing electron multiplication between saidapertured electrode and one of said additional electrodes by secondaryemission from each of the last said electrodes, an output circuitconnected between said apertured electrode and one of said additionalelectrodes and reso nant to the frequency of interception and passage ofsaid electrons, and means for biasing the electrodes connected to-saidoutput circuit with respect to one of said additional electrodespositioned intermediate said two connected electrodes comprising aconnection intermediate the ends of said output circuit and a source ofpotential connected between said connection and said one additionalelectrode.

4. In a frequency multiplier, an electron discharge tube having acathode, a beam focusing electrode, horizontal and vertical beamdeflecting means and a plurality of accelerating electrodes, one of thelast said electrodes having apertures therein through difierent ones ofwhich in electron beam may be successively projected, a. source ofsingle phase alternating current, means for splitting said alternatingcurrent into at least two phases and acting upon the beam deflectingmeans for timing recurrent rotative deflections of the electron beam,means includin said apertured electrode for producing secondary emissionand multiplication of electrons in that portion of the beam beyond theapertured electrode, a polarized output circuit for said discharge tubeconnected to said means for producing secondary emission andcharacterized in that an alternating current may be produced therein ata frequency determined by the rate of interception of said electron beamby different por- "tions "of said apertured electrode between theapertures thereof, and further characterized in that said output circuitincludes an inductance having a center-tap and a capacitance shuntingsaid inductance, the center-tap being connected through a source ofdirect current potential to a ring-shaped anode, and the terminals of.the inductance being connected respectively with different ones of theelectrodes comprised in the means for producing secondary emission,whereby said output circuit is made resonant to the frequency of thepassage of electrons through said apertured electrode.

\5, A frequency multiplier in accordance with claim 4 furthercharacterized in that there is provided a source of magnetic flux thelines of which co-mingle with said electron beam beyond said aperturedelectrode and have a trend parallel to the direction of said beam.

6. A frequency multiplier in accordance with claim.4 furthercharacterized in that said output circuit is tuned to a frequencyharmonically related to the frequency of said alternating current thatacts upon the beam deflecting means.

7. In an oscillation generator and frequency multiplier, a source oftwo-phase current of. a fundamental frequency, a target having aperturesdisposed in circular formation, the number of apertures being determinedby the multiplication factor to be applied to the fundamental frequency,a cathode ray tube having said target as one of its anodes, and havingother electrodes serving as an electron gun, beam deflecting means forso controlling an electron discharge from said gun as to direct the beamsuccessively through diflferent ones of the apertures in said target,connections from said source of two-phase current to said beamdeflecting means for controlling said beam, and secondary emission meansincluding additional electrodes on the opposite side of the target withrespect to said electron gun and said apertured target and including atuned output circuit interconnecting the additional electrodes and thetarget for producing an amplified alternating current at the desiredmultiple frequency, and comprising a center tapped inductor and acapacitor and a source of a biasing potential connected between saidcenter tap and a ring shape electrode intermediate said secondaryemission means. a

8. In an oscillation generator, an electron discharge device having acathode, a beam-focusing anode, and an accelerating anode, horizontaland vertical beam deflecting means for said device, means including asource of alternating current and a phase-shifting device for soenergizing said deflecting means as to effect a rotary movement of theelectron beam within said discharge device, a shield having a pluralityof holes arranged in the path of said electron beam, means foraccelerating electrons after they are shot through said shield, saidmeans comprising additional electrodes in said device, and meansincluding a source of energy and an output circuit comprising acenter-tapped inductor and a capacity connected with said shield andwith said additional electrodes for producing secondary emission'fromsaid shield said source of energy being connected between said centertap and a ring shape electrode positioned between said secondaryemission electrode and for generating in said output circuitoscillations of a frequency which is determined by the speed of rotationof the electron beam and by the number of holes in said shield.

JOHN EVANS.

